Network performance analysis and manuever model for overtaking assistant service using wave

We present network requirements for an overtaking assistant service using wireless access in vehicular environment (WAVE). Currently, DNPW has been proposed as a representative overtaking assistant service with vehicle-tovehicle (V2V) communication. In order to analyze its network performance, we construct a maneuver model for an overtaking system. According to this model, we configured a scenario for network simulation based on the 802.11p WAVE standard. The results confirm that a radio range for overtaking needs only a single hop without routing methods. Moreover, we propose an additional safe distance for the communication delay generated by an increase in the numbers of neighboring vehicles. And for high priority activity of safety services, we present a proper access category (AC) of enhanced distributed channel access (EDCA). These analysis results should be tested considered in real safety service systems that use V2V communication.     

�����г�ʱ��ɿ��Եij����Ż�����

行程时间的不确定性是影响货运车队路径选择的一个重要因素，特别是对于要求货物准时送达的配送任务（例如商品混凝土的配送），提出了在车辆调度中考虑由拥挤路段交通流量波动引起的行程时间不确定性的方法，建立了考虑行程时间可靠性要求的车辆优化调度数学模型，给出了相应的启发式算法，通过算例介绍了该模型和算法的应用。结果表明配送总成本随行程时间可靠性要求的提高而增加。     

A Report on the State-of-Affairs on “Application of Multibody Computer Codes to Vehicle System Dynamics”

This report gives a preview to a state-of-the-art paper and a special session which are devoted to the problem of the applicability of multibody computer codes to vehicle system dynamics. These activities were initiated at the 11th IAVSD Symposium 1989 in Kingston, CAN, followed by a workshop in Herbertov, CSR, and to be reported at the 12th IAVSD Symposium in Lyon, 1991. The concluding documentation will be a special issue of the VSD journal. The status of this report is what has been achieved up to May 1991.     

An Evaluation of Passive Automotive Suspension Systems with Variable Stiffness and Damping Parameters

Passenger discomfort, suspension working space and dynamic tyre loading parameters are calculated for different combinations of spring stiffness and damping coefficient representing the suspension system in a quarter car model subject to realistic random disturbance inputs from roads of widely differing quality. Sprung and unsprung masses and the tyre vertical stiffness and damping coefficient employed derive from a current production car. Designs which are best for the specific conditions represented are identified and their performance properties in other (off-design) conditions are considered, and conventional design is explained as the inevitable consequence of the need to compromise if fixed suspension parameters are used. Performance improvements possible if variable parameters can be employed are evaluated as a function of the ranges of variability provided, and a stratagem for controlling parameters is proposed.     

A structural and empirical model of subsistence activity behavior and income

This paper develops a structural and empirical model of subsistence activity behavior and income. Subsistence activity decisions (work participation and hours of work decisions) and income have an important bearing on activity and travel behavior of individuals. The proposed structural model represents an effort to analyze subsistence activity behavior and income earnings to support a better understanding, and reliable forecasting, of individual travel behavior. The empirical model formulates and estimates an integrated model of employment, hours of work and income which takes account of interdependencies among these choices and their structural relationships with other relevant variables. Social factors that inhibit an individual's employment and work hours decision and affect an individual's income are incorporated in the model. A sample of households from the Dutch National Mobility Panel is used in the empirical analysis.     

New generic mathematical model to predict hydrodynamic interaction effects for overtaking maneuvers in simulators

To improve the formulation of ship–ship interaction forces and moments in a mathematical model of a ship maneuvring simulator, we developed a new generic mathematical model for the overtaking maneuver. This process involves using the numerical results, which provide a potentially complete set of data from which (within the constraints of the numerical modelling) everything necessary can be acquired. We found that the new generic mathematical model is as accurate as the numerical model. It is also more accessible to a navigator, master, or pilot, who could use it on a palmtop computer by keying in a few numberical estimates of the size, position, and speed of the neighboring ship and receive almost instant aneous results, giving time for a refined strategy to be validated if necessary. These results can also readily be used by simulation program developers to simulate the worst possible scenarios.     

Extension of Newell's dispatching policy to the case of sensitive demand

This paper has extended Newell's dispatching policy to the case of sensitive demand which is characterized by a linear mode split model with two major factors, wait time and transit fare. Three objective functions both with and without vehicle capacity constraint are analyzed, including profit maximization, maximization of a combination of net user benefit and operator profit, and maximization of net user benefit subject to a deficit constraint. Closed-form solutions associated with various system parameters are obtained. It is shown that under sensitive demand conditions the optimal dispatching rate is approximately proportional to the square root of the total demand rate, if vehicle size is not binding and it is strictly proportional to the total demand rate, if vehicle size is binding.     

Carrier selection in a RO/RO ferry trade Part 1. Decision factors and attitudes

The choices faced by shippers are generally complex. Typically, the shipper is presented with a range of alternative carriers, each of which has its individual strengths and weaknesses. A survey of companies purchasing shipping services in an overnight RO/RO ferry trade was conducted to identify their priorities and to help understand and the decision-making process. The shippers were found to be conservative decision makers with a strong emphasis on quality of service.     

Modeling oil spills in a river—lake system

A general model shell, ROSS3, is developed for simulating oil spills in complex river systems using techniques which have not been previously exploited in oil spill models. ROSS3's new approach has several advantages over the approach to model oil spills in the past: (a) The use of a time-varying boundary-fitted coordinate system that allows accurate accounting for complex river/lake boundary as well as the river boundary changes as its water levels fluctuate; (b) The ability to confine two-dimensional hydrodynamic computations to a limited river reach; (c) The ability to interactively layout the channel networks for setting up the model, define extra cross sections to increase the accuracy if needed, in addition to the traditional data entry and visualization interfaces.ROSS3 is a two-layer two-dimensional oip spill model that can simulate the mechanism of advection, horizontal diffusion, mechanical spreading, shoreline deposition, evaporation, dissolution, vertical mixing, resurfacing and sinking. In ROSS3 spilled oil may be a surface slick or suspended oil droplets, or a combination of both. Both free surface and ice cover conditions can be simulated. The flow of conditions can be varied and the unsteady flow model can be run within ROSS3 to simulate the flow conditions in both the river and the lake. The ice conditions can be added or removed from the model input using easy interactive procedures.     

The choice of ship size on deep-sea general cargo routes

The introduction of unit load methods, particularly the cellular container system, has been associated with a large increase in ship size on some of the world's major general cargo routes. In this sector, ship size is determined by a set of interactions between handling performance, route length, traffic flow, itinerary, requirements for frequent and regular service, port costs and general system organization. This paper explores these relationships to identify major influences and to consider the prospects for further growth.